下面是一个在Java 8中实现这一功能的SSCCE

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

public class IterableToCollection {
    public interface CollectionFactory <T, U extends Collection<T>> {
        U createCollection();
    }

    public static <T, U extends Collection<T>> U collect(Iterable<T> iterable, CollectionFactory<T, U> factory) {
        U collection = factory.createCollection();
        iterable.forEach(collection::add);
        return collection;
    }

    public static void main(String[] args) {
        Iterable<Integer> iterable = IntStream.range(0, 5).boxed().collect(Collectors.toList());
        ArrayList<Integer> arrayList = collect(iterable, ArrayList::new);
        HashSet<Integer> hashSet = collect(iterable, HashSet::new);
        LinkedList<Integer> linkedList = collect(iterable, LinkedList::new);
    }
}

试试Cactoos的StickyList:

List<String> list = new StickyList<>(iterable);

两个评论

There is no need to convert Iterable to Collection to use foreach loop - Iterable may be used in such loop directly, there is no syntactical difference, so I hardly understand why the original question was asked at all. Suggested way to convert Iterable to Collection is unsafe (the same relates to CollectionUtils) - there is no guarantee that subsequent calls to the next() method return different object instances. Moreover, this concern is not pure theoretical. E.g. Iterable implementation used to pass values to a reduce method of Hadoop Reducer always returns the same value instance, just with different field values. So if you apply makeCollection from above (or CollectionUtils.addAll(Iterator)) you will end up with a collection with all identical elements.

尽管如此，不要忘记所有的集合都是有限的，而Iterable没有任何承诺。如果某个东西是Iterable，你可以得到一个Iterator，就是这样。

for (piece : sthIterable){
..........
}

将扩大到:

Iterator it = sthIterable.iterator();
while (it.hasNext()){
    piece = it.next();
..........
}

it.hasNext()不需要返回false。因此，在一般情况下，您不能期望能够将每个Iterable转换为一个集合。例如，你可以遍历所有正自然数，遍历带有循环的东西，反复产生相同的结果，等等。

除此之外:Atrey的回答很好。

从CollectionUtils:

List<T> targetCollection = new ArrayList<T>();
CollectionUtils.addAll(targetCollection, iterable.iterator())

下面是这个实用方法的完整源代码:

public static <T> void addAll(Collection<T> collection, Iterator<T> iterator) {
    while (iterator.hasNext()) {
        collection.add(iterator.next());
    }
}

在JDK 8+中，不使用任何额外的库:

Iterator<T> source = ...;
List<T> target = new ArrayList<>();
source.forEachRemaining(target::add);

编辑:上面的是迭代器。如果你在处理Iterable，

iterable.forEach(target::add);